Cells in the pars reticulata of the substantia nigra in the basal ganglia of monkeys have been studied to determine their relationship to the initiation of visually-guided saccadic eye movements. Some cells are related to the initiation of the saccadic eye movements themselves, others to the visual stimulus which is the target for the saccade. Most visual responses are modulated depending on the use of the visual stimulus by the monkey; the decreased response is greater when the monkey uses the stimulus and is frequently eliminated when the monkey uses another distant stimulus as the target for a saccadic eye movement. These cells may represent the output of the basal ganglia to the oculomotor system. Since the pars reticulata cells project to the superior colliculus, they may act on the oculomotor system by acting on the saccade-related cells in the superior colliculus.